JP 2006-254662A describes a rotor in which plural projection parts are formed around a central hole part of a main core. Specifically, the projection parts are projected from the inner wall of the central hole part toward the central axis of the main core. When a shaft of a rotary electric machine is pressingly fitted inside the central hole part, the shaft and the main core are in contact with each other with a contact area. The contact area can be made smaller, due to the projection parts, so the press fitting load of the shaft can be reduced.
In JP 2006-254662A, the rotor has an opening part passing through the main core in the thickness direction. The opening part is located on the outer side of the projection part in the radial direction. Thereby, when the shaft is press-fitted inside the central hole part, the projection part can be displaced outward in the radial direction, and a portion between the projection part and the opening part is deformed. Thus, the press fitting load of the shaft can be further reduced.